Power transmission



April 1943- D. VBIERMANN 2,316,390

POWER TRANSMISSION Filed Dec. 18, 1940 4 Sheets-Sheet l INVENTOR.

April 13, 1943. D. BIERMANN POWER TRANSMISSION FiledDec. 18, 1940 4 Sheets-Sheet? INVENTOR.

April 13, 1943. D. BIERMANN POWER J'IRANSMISSION 4 Sheets-Sheet 3 Filed Dec. 18, 1940 00 riven) I April f D.- BIERMANN 2,316,390

POWER TRANSMISSION Patented Apr. 13, 1943 l UNITED STATES PATENT OFFICE POWER TRANSMISSION David Biermann, Hampton, Va. Application December 18, 1940, Serial No. 370,659 1 Claim. (01. ii-189.5)

The present invention relates to power transmitting apparatus, and more particularly to hydro-mechanical speed changing power transmissions.

The invention herein disclosed is of the type of transmission in which two or more fluid clutches are used in conjunction with planetary gears to obtain certain desired operating characteristics. The fluid clutches are used to transmit the driving torque in a smooth manner to members geared or directly coupled to the driver shaft in such a way that speed reduction'and torque multiplication continuously changes under certain operating conditions as will be described hereinafter. v

In hydro-mechanical transmissions for automobiles heretofore developed of the type under consideration the most common forms utilize a single fluid clutch'and a multiple of gears which are shifted either manually or by auxiliary control means to obtain different torque and speed relations. These transmissions have been extremely complicated, almost without exception, and they lack complete smoothness of operation when the gears are shifted.

To meet the requirements of a transmission for use with modern automobiles, I have devised a simpleeutomatic mechanism which can be produced at a cost comparable with that of a conventional transmission and yet which is capable of providing nearly ideal: operating characteristics.

Accordingly, a primary object of the present invention is to provide novel hydro-mechanical transmissions of extremely simple, rugged, and low ,cost construction, adapted for use with modem internal combustion automobile engines.

Another object of the invention is to provide hydro-mechanical transmissions embodying novel automatic and manual control mechanisms.

Still another object of the inventionis to provide means for progressively changing the gear ratio in a smooth uninterrupted manner, said gear change being a function of the speed of the automobile and the torque load on the engine.

Yet another object is to providemethods for easy shifting of mechanical clutches.

A further object is to provide means for manually locking the transmission in low speed.

Other objects of the invention are such as may be attained by a utilization of the various combinations and principles hereinafter set' forth in the varied relations to which they are obviously applicable by those skilled in the art.

The invention will be best understood and further objects will appear from a study of the following detailed description taken in connection with the accompanying drawings, with the understanding, however, that the invention is not confined to any strict conformity with the showing in the drawings, but may be changed and modified as long as such changes mark no material departure from the salient features of the invention as expressed-in the appended claims.

In the drawings:

Figure 1 isa vertical section taken longitudinally through a preferred embodiment of my invention.

Figure 2 is a plan view of the remote control lever-shown linked to the control system of the transmission.

Figure 3 is a vertical section taken through the remote control lever shown in Figure 2.

Figure 4 is a vertical section taken on line 4-4 of Figure 1.

Figure 5 is a partial horizontal section taken on line 5-5 of Figure 1.

Figure 6 is a partial horizontal section taken on line 6-6 of Figure 1. I

[Figure 7 is a vertical section taken on line 7-1 of Figure 1.

Figure 8 is a vertical section taken on line 8-8 of Figure 1.

Figure 9 is a diagram showing the component velocities of the fluid as it passes through section- 55 of Figure 1.

Figure 10 is the calculated torque and efficiency characteristics of the transmission basedon the velocity diagram given in Figure 9.

Figure 11 is a partial vertical section taken longitudinally through the rear part of the transmission showing an alternative arrangement of the mechanical clutch and reversing mechanism.

Figure 12 is a vertical section taken along line i2--i2 of Figure 11.

In the drawings briefly described above in which like reference characters designate like parts, the transmission is shown completely assembled in Figure 1 and adapted to be mounted in any manner between a source of power and a driven shaft, with its forward (left) end arranged to be driven from saidpower source and its rear (right) end adapted to transmit multiplied torques to said driven shaft. 1

The transmission is mounted within a supporting housing made up of two sections, the front housing 94, and the rear housing 86, separated by diaphragm 85. Contained within housing 84 is a unique fluid coupling or a combination radial and axial turbine which receives torque from driving shaft H4 and transmits said torque into the rear housing 96 by means of either or all of three concentric shafts which will be explained later. Contained within rear housing 95 are the mechanisms for multiplying the torque, reversing the rotational direction, clutching and declutching as will be explained more fully presently.

Fluid coupling or turbine.-The fluid coupling is comprised of four separate members: driving element I3, which provides a container for driving fluid; first intermediate driven element I4; second intermediate driven element I5; and the final driven element I6. These four members are all independently rotatable about an axis also common to the drive shaft H4; and they are all supported directly or indirectly by bearings contained within front housing 94 and diaphragm 95.

Referring to Figures 1, 4. 5, and 6, it may be seen that a number of curved fluid passages I! are formed in driving element I3. Each passage I1 is separated from the adjacent passage by radial vane I8, all of which are fastened to element I3. Island I9 is carried by vanes I8. Passages II are arranged to receive fluid in an axial direction at a'short radial distance from the axis of rotation, and to turn the fluid approximately 180 degrees to discharge It at a greater radius. Thus rotational motion transmitted from element I3 to the fluid contained in passages II sets up a centrifugal force acting to circulate the fluid in a combined radial-axialrotational direction.

Fluid leaving passages IT in element I3 enters outer passages 28 formed in element I4 and impinges on outer vanes 2| carried between rim 22 and island 23, which transmits torque to the hub of element I4 and to shaft 24.

Fluid leaving outer passages in element I4 enters outer passages 25 formed in element I5 and impinges on outer vanes 26 carried between rim 21 and island 28, which transmits torque to the hub of element I5 and to shaft 29.

Fluid leaving outer passages 25 enters passages 30 formed in final driven element I6 and impinges on radial vanes 3| carried by element I6 which transmits torque to sleeve shaft 32.

Island 33 is carried by vanes 3i and forms one side of passages 30. Fluid entering passages 30 at the outer entrance is turned through approximately 180 and discharged at a smaller radius in a combined rotational and axial direction.

Fluid leaving passages 30 enters inner passages 34 formed in element I5 and impinges on vanes 35 carried between island 28 and the hub of element I5.

It is quite obvious to those skilled in the art that the velocity of fluid circulation and the directions of flow throughout the cycle will depend upon a number of variables such as: relative rotational velocities between the four members of the fluid coupling, the shape and angles of the various vanes, and several other minor variables. It is also quite clear that the amount of torque transmitted at any instant from the driving element I3 to any of the driven elements will depend upon the rate of change in angular momentum of the fluid times the radius to the mean flow passageway; which will depend in turn upon the variables previously mentioned. By gearing elements I4 and I5 at certain diflerent ratios to element I5, which is directly coupled t0 the final driven shaft, and by setting vanes 2|, 26, 35, and 31 at certainangles it is possible to obtain very desirable characteristics of the transmission which will be explained more fully later.

Torque multiplying gears.Referring to Figures 1, 7, and 8, means for multiplying and transmitting the applied torque to the final driven shaft are illustrated. In the description of the fluid coupling the separate torques transmitted to elements I4, I5. and I6 was seen to be passed on to concentric shafts 24, 29, and 32 respectively. Shaft 32 is directly coupled to spider l5. planet shafts 39, spider 40, shaft 4I, and spline teeth 42. When dog clutch 43 is set for forward operation, spline teeth 42 engage with teeth 44 which couples shaft 4i to driven shaft 45, since spline teeth 45 and 41 are constantly engaged. Thus element I6 is directly coupled to driven shaft 45 for forward operation.

Shaft 24 is directly connected to sun gear 48 which meshes with planet gears 49 carried on shafts 39. Planet gears 49 also mesh with ring gear 50, which is arranged to transmit the reaction torque to the frame through the over running brake assembly 5i, brake teeth 52, engaging pawl 53, brackets 54 to housing 86. Thus the torque carried by shaft 24 is multiplied by gears 48, 49,'and and transmitted to the driven shaft through a means previously described: viz. shafts 39, 4I, etc.

Sleeve shaft 29 is directly connected to sun gear 55 which meshes withplanet gears 56 which in turn are carried on spider shaft 39. Planet gears 56 also mesh with ring gear 51 which transmits the reaction torque to housing diaphragm by way of over running brake assembly 55. Thus the'torque carried by shaft 28 is multiplied by gears 55, 56, and 51 and transmitted to the driven shaft through a means previously described; viz. shafts 39, 4|, etc.

In the above description the driving torque was seen to enter the transmission from shaft H4 and divided into three parts while passing through the fluid coupling. The division of torque was seen to depend upon the detail design of the fluid coupling as well as the relative rotational speeds of the four elements. In the description of the gearing it was seen that the three fluid coupling driven elements (I4, I5, and I6) were all coupled, either directly or through torque multiplying gears, to the driven shaft 45. This means that the three elements I4, I5. and I5 will rotate at different speeds; the values will depend upon the gear ratios employed. It was seen that the torque reaction of two geared drives was taken out to the housing through over-running brakes, which means that these geared drives can produce driving torque only in one direction (the same direction as the applied torque). In other words the torques supplied to the driven shaft 45 by the two geared drives and one direct drive can only add. As soon as any of the torque values in either of the geared drives changes to a minus value it ceases to exist. Obviously, when either of the over-running brakes 51 or 58 start to free wheel, the entire geared assembly of each associated drive and its attached fluid coupling element will also free wheel or rotate as a unit at substantially the same speed as driving element I3. When both the geared drives are free wheeling then the driving torque driven shaft 48 will tend to become equal except for a small slippage in the fluid coupling.

The purpose of the two intermediate coupling elements l4 and i6 ancrtheir associated torque multiplying gears is to multiply the applied torque for conditions of operation when driven element i8 is stopped or rotating at any speed substantially lower than that of driving element II. All the torque entering the fluid system through shaft H4 must also pass out through either or all of shafts 24, 29, and 82. As previously mentioned, the division of torque will de-, pend upon the relative rotational speeds of the four fluid units and upon the detail design. Up to the moment of free wheeling, the relative rotational speeds of the three driven elements I4, 15, and i8 is definitely determined by the gear ratios of the two planetary gear trains. Thus if shaft 24 is geared to shaft 4| by a train of gears having a ratio of 0.83 then element M will rotate at three times the speed of element i8; and if shaft 29 is geared to shaft 4| by a train of gears having a ratio of 0.67 then element is will rotate at 1.5 times the speed of element I6. The gear ratios employed will largely determine the division of torque in the fluid coupling at various ratios of the driven to driving shaft speeds. because they determine the relative speeds of driven elements I4 and it to the driving element is; which in turn determines largely the angles at which the fluid leaving passages impinges upon blades 2| and 2B.

The other important factor determining the division of torque in the fluid coupling is the geometric angle settings of the various blades. In Figure 9 is a diagram showing the component velocities of the fluid as it leaves passages ii, 20, and and as it enters passage 30 for different ratios of the driven to driving shaft speed (Nu/N13) This diagram is based on certain assumed gear ratios and blade angle settings and does not apply to other values. The

change in the angle and the velocity of the resultant flow as it passes through each passage is a measure of the torque transmitted to that element. Thus when N1a/N13=0. a large positive torque is transmitted to element l4, none to element i5. and a negative torque to element It. Since the sum of the torques leaving the system must equal the torque entering, then Ql4Ql8=Ql3 or Q1l=Q13+QlB- This means that the torque transmitted by element l4, which 1 will be multiplied 3 times, is greater than the applied torque; and that transmitted by element it, which is not multiplied, will act against that transmitted by element It. For N1e/N1a==.2 a large portion of the applied torque is transmitted by element l4, a small portion by element I5. and a small portion by it in the reverse direction. At N1a/N1a=-.4 most of the torque is taken out through element l5 and multiplied by 1.5. At Nl6/Nl3=.6 the torque in element I4 is seen to be equal to about zero; over-running brake ill will then release ring gear 50 so that element l4 will float in the fluid stream passing through it. Element i5 is seen to be taking most of the load while element It is still transmitting a small negative torque..

At Nl8/Nl3='.8 element I6 is seen to have taken over the load from element I5. Over-running brake 58 will then release ring sear 51 and allow element It to float in the fluid stream passing through it. At N1s/Nn='1.0 all four elements are seen to be rotating as a unit. 7

In Figure 9 it may be noted that the axial component of flow diminishes as NfO/Nls increases. This can be explained by the fact that as element 58 speeds up a centrifugal force is generated in the fluid contained within passages which tends to counteract that gen.- erated in passages i1 leaving less force or pressure to circulate fluid through the system. As NlO/Nlil approaches unity the flow of fluid approaches zero and the entire fluid coupling together with the fluid and all the rotatable parts of the transmision rotates substantially as a unit. Under such conditions the efliciency also approaches unity. A small slippage of the fluid coupling is necessary in order to convey torque, however. but it is ordinarily small for high rotational speeds.

In Figure 10 is the calculated torque and efliciency characteristics, for the transmission based on the velocity diagram given in Figure 9. The starting torque applied to the driven shaft is seen to be over four times the driving torque. This progressively decreases until the driven and driving torques become equal at a value of N driven/N driving of 0.8. The efflciency is seen to average over percent for 80' percent of the transition range. Control mechanisms-Means for actuating mechanical clutch 43 is shown in Figures 1, 2, and 3, together with other mechanisms for controling the operation of the transmission. Control lever 6|, which would be located convenient to the operator, is supported on lugs 62 attached to column 63 by means of pin 84. Column 63 is rotatable within fixed sector frame 65 and is arranged to transfer one component of the motion of lever 8| to lever 86. Lever 68 is connected to clutch lever 81 by means of link 68, pins 69 and 10. Lever 81 is pivoted on lugs 1|, attached to housing 96. by means of pin 12; and is provided with lug it which flts into slot 14 of clutch 43. Movement of control lever 6| to the left from the neutral (N) position shown in Figures 1 and 2 moves clutch 43 to the right and engages spline teeth 42 with teeth 44 thereby coupling, shafts 4| and 45 for forward or high (1-!) operation.

Spline teeth 42 and 44 cannot be engaged, however, unless shafts 4| and 45 are both stationary. Although shaft 45 is stationary when the automobile is stopped, shaft 4| would not be unless special provisions were incorporated to stop said shaft 4| during the shifting period. Braking of shaft 4| is accomplished as follows:

Control lever .Si is provided with lug 15 which is arranged to fit in slots 16 formed in sector frame 65. Lug 75 serves to locate lever 6| and also necessitates rotating said lever 6| about pin 64 before a shift from one position to the other can be made. Rotation of lever 6| about pin 84 transmits longitudinal movement through pin 1! to valve stem 18, and opens valve 19 for the passage of fluid to or from ports 80, 8|, and 0. In the present invention provisions are made for using vacuum for actuating the braking device, the source of said vacuum could be the manifold of the engine or a'vacuum pump connecting with port 80. Positive pressure of air or oil could be used with a slightly different arrangement of the parts. Port 8| is connected with pipe 82, shown in Figures 1 and 7, which is tapped into cylinder 93. A reduction in pressure in space 04 causes air to flow through port 95 and move piston 05 and rod 81 which clamps brake band 60 on to drum 99 causing said drum to lock. Since drum "is fastened to planet shafts 39 shaft 4| is also stopped. Lever BI is then shifted to a new position and lug I5 is allowed to slide into a slot 15 through the action of spring 93. This closes port 60 and allows air to enter valve 19 through port H and slot 90 which equalize pressure on the two sides of piston 86. Spring II then returns rod 01, piston 65, and brake band 69 to their normal or free position. Nut 92 is provided for adiustment.

Reversing the direction of rotation of driven shaft 45 may be accomplished in any number of obvious ways, two of which will be described: In Figure 1 is shown one means. Although this is seen to be a simple solution it may not be the best from the standpoint of ease of shifting the dog clutches necessary, the gear ratio may not be correct for the best operational characteristics. An alternative reversing mechanism is shown in Figure 11 which does not have the obiections noted above. The reversing mechanism shown in Figure 1 will be described first.

For reversing the direction of rotation of shaft 45, shown in Figures 1, 2, and 3, lever 6| is moved until lug 15 fits into slot 16 marked R. This motion is transferred to lever 61 and dog clutch 43, which is moved to the left, engaging spline teeth 91 with spline teeth 98. Teeth 98 are fastened to shaft 99 which is in turn connected with ring gear 50. During this shifting operation, motion from lever 61 is transferred to lever I00 I see also Figure 8) through link IOI. This motion is carried to engaging pawl 53 through sleeve I02 carried on shaft I03, said pawl 53 is disengaged from teeth 52 of the over-running brake 5|.

Motion from lever I00 is also carried to lever I04 through link I05, said lever I04 is directly connected to shifting pawl I06 in the same manner as is lever I00 connected to pawl 53. Lever I04 and pawl I06 are mounted on shaft I01 which is supported by lugs I06. Shifting lever iii to the R. position engages pawl I06 with teeth I09 mounted on drum 09.

With ring gear 50 coupled to driven shaft 45, and planet shafts 39 locked, torque from element I4 is transmitted through shaft 24, sun gear 40, to planet gears 49 and applied to ring gear 50 in a reversed direction and at a multiplied value. The torque reaction is carried to diaphragm 9.5 through drum 89, teeth I09, pawl I06, and lugs I06.

Since planet shafts as are locked, then fluid coupling element I6 is likewise locked. Element I5 is prevented from rotating in the same direction as element I4 because of the locking of planet shafts 39 and the over-running brake 58, which prevents rotation of ring gear 51 in a direction opposite to that of element I5.

The multiplication of torque for reverse will be greater than the gear ratio because there will be additional torque multiplication in the fluid coupling. Referring to Figure 9 it can be seen that if the rotational component of the fluid is reversed in direction in traveling through passages 20, then the impact on vanes 2| will be greater than that applied by vanes I8. The reversed rotational component will be taken out by vanes ll, since they will 'be fixed, and the torque reaction of the fluid coupling will be carried out to diaphragm 95 through pawl I06.

Means for locking driven shaft 45 to prevent the vehicle from moving when it is parked is incorporated in this transmission. Movement of control lever III to the position marked P (see Figures 1, 2, and 3) effects coupling of shaft 45 with shaft 4I through the engagement of spline teeth 41 with teeth 46 and teeth 48 with teeth 42. Shaft H is looked through the action of pawl I06 engaging with teeth I09.

In case it is desired to lock the transmission in low gear in order for the engine to brake the vehicle when descending steep grades, control lever 6| can be moved to position marked L. This action engages pawl 53 with teeth III carried on ring gear 50 and prevents rotation of said gear 50. Element I4 is then forced to rotate at a speed several times greater than that of shaft 45 which will induce a fluid circulation in the coupling in the same direction as for normal high speed operation by virtue of the angle settings of blades 2| and 31. With circulation set up the interaction of the fluid on the several blades in the system will be such as to transmit torque from one element to the other tending to equalize their speeds. The engine will thereby be speeded up which will produce the desired braking effect.

In shifting from one control position to the other, provisions have been made for preventing relative movement of any of the mating parts except for the low-lock position. Another provision to facilitate the engagement of pawls 53 and I06 with teeth 52 and I09 respectively is also incorporated. In Figure 8 it may be seen that pawl 53 is mounted on shaft I03, which is arranged to slide axially a limited distance as well as to rotate. Springs II2 keep shaft I03 centered between lugs 54 when pawl 53 is not engaged. In shifting control lever 6|, if pawl 53 does not align itself with slots formed between teeth 52, shaft I03 will slide axially in either direction by virtue of the centering action of pawl 53 (which has a knife edge) without the application of excessive force. Although not shown, pawl I06 is also provided with this feature.

The same principle'is also applied to dog clutch 43 to facilitate shifting see Figure l). A large clearance is provided between teeth 46 and 41. Springs II3 keep teeth 41 centered between teeth 46 when clutch 43 is not engaged. When shifting, clutch 43 may rotate slightly in either direction against the action of springs II3 so that either teeth 44 may easily engage teeth 42 or teeth 91 may engage teeth 98.

There is a certain problem connected with releasing of either of the pawls 53 or I06 or the clutch 43 against the drag of the fluid coupling. Provisions are incorporated to reduce the friction to a minimum. Pawls 53 and I06 are both wedge shaped so that any side force will tend to disengage them and thereby nearly offset the effect of friction. Similarly, teeth 98 and 91 are cut on a spiral in such a direction that the applied torque will tend to disengage them; likewise are teeth 42 and 44. The pitch is so calculated that the clutch will remain engaged under operating conditions.

If the above provisions were not sufficient to enable easy shifting a. booster cylinder could easily be attached to lever 61.

The alternative reversing mechanisms previously mentioned are shown in Figures 11 and 12, which would replace the parts shown in Figure 1 to the rear (or right) of section 8 8, and also eliminate pawls 53 and I06 and their actuating mechanisms. The same parts shown in both Figures 1 and 11 are designated with the same character.

Torque from shaft ll is transmitted to clutch III through spline teeth II! and III fastened to shaft 4| and clutch II! respectively. For forward operation clutch II! is movedto the right by action from lever I It and coupled with driver shaft 4! through mating of spline teeth III with teeth Ill. Lever .I-Ia is pivoted on shaft I20 which is in turn fastened to hous- Ing 86. The force required to shift clutch III is transmitted from lever H8 to lug I 2I which fits in slot I22.

For reverse operation clutch II! is moved to the left until gear I23 meshes with gear I24.

The torque is then transmitted to shaft I28, gear I20, idler gear I21, and gear I28 which is fastened to driven shaft 45. shaft I2! is supported by bearings formed in housing 88 and diaphragm I20. Idler gear I2! is carried. on housing "by means of shaft I80.

The torque reaction from shaft 89 is carried out to housing 88 through over-running brake assembly BI supported in diaphragm I28.

In Figure 12 is shown in detail the means for providing easy shifting of clutch iii to either the forward or reverse positions. It may be noted that a large clearance is provided between teeth H8 and Ill, and that said clearance is,

equalized between the adjacent teeth faces for neutral position by means of springs I3I acting on pins I32. Springs I3I are compressed by 4 screws I33. In shifting clutch iii, if teeth I" do not mate with teeth IIB then the wedge shaped ends of said matingteeth will guide them into position by rotating clutch III against springs Iti. This procedure also applies to shifting into reverse.

Operation the transmission on an automobile.-This transmission has particularly desirable operating characteristics for motor vehicles in general. Its freedom from shifting of gears or clutches while driving in trafllc and its extreme smoothness in operation combined with its high accelerating qualities makes it outstanding.

Before the engine is started, control lever BI is placed in neutral position (N). The engine is r '5 Resumption of forward speed is accomplished by increasing the engine speed, with brakes released.

It-may be desirableto obtain a large braking eifect from the engine when coasting down a steep hill or mountain side. In this event lever ll is moved to low position, marked L. This action forces the power through oneset of speed up, which results in the desired braking effect.

In parking on a hillside it is often desirable to lock the wheels by a means more positive than the parking brake affords. This may be accomplished by moving lever 8| to the position marked P.

Having described certain preferred embodiments only of my invention, what is desired to be secured by Letters Patent and claimed as new is:

A rotary power'transmission comprising a driving shaft; a driven shaft; a supporting fixed housing: a rotatable fluid tight housing coupled to said driving shaft; a centrifugal pump contained within and fastened to one end of said rotatable housing; a centrifugal motor facing then started and run at a low rotational speed.

If it is desired to run in reverse, lever Si is moved to position marked R. As soon as the shift has been completed there will be a slight tendency for the vehicle to roll backwards due to the transmission of a small torque through the fluid coupling. Increasing the engine speed increases this torque until the proper speed is reached. Stopping is accomplished by slowing down the engine speed and applying the brake.

Lever 6! can then be shifted to the high position (H). The engine speed canthen be increased to any reasonable value depending upon the amount of starting acceleration desired. In any event the speed of the vehicle will increase in a smooth uninterrupted manner until the desired value is reached; whereupon all rotatable elements in the transmission will be rotating at slightly less than engine speed; for which the efficiency will be nearly unity.

In slowing down, the engine throttle is closed. Power from the wheels is then transmitted back through the transmission to the engine which acts to retard the forward speed. As the speed of the vehicle approaches zero the amount of torque transmitted by the fluid coupling also approaches zero so that the engine isfree to run at idling speed. Stopping of the vehicle is said pump at the opposite end of said housing and rotatable independentlyof but cooperating with said pump for the purpose of transmitting torque from said pump to said motor through the interaction of fluid on blades carried by said pump and motor; two axial motors disposed between said centrifugal pump and centrifugal motor driven by the action of fluid impinging on blades carried by said axial motors, said fluid being circulated through the planes of said axial motors by said centrifugal pump and centrifugal motor; a central shaft connecting the axial motor which is adjacent to the pump to a sun gear of a planetary gear train; a plurality of planet gears meshing with said sun gear; a plurality of planet shafts carrying said planet gears and supported by a spider: a rotatable shaft coaxial with said driving and driven shafts connecting with said spider; a mechanical dog clutch arranged for coupling said spider and shaft with said driven shaft: a ring gear meshing with said planet gears and supported by a sleeve shaft encasing said spider shaft; one-way brake carried concentric with said ring gear sleeve shaft; a manually actuated dog clutch arranged for engaging with said oneway brake so that torque could be transmitted in a direction opposite to that of the driving torque from said ring gear to said fixed housing; a sleeve shaft concentric with said driving and driven shafts connecting said axial motor which is adjacent to said centrifugal motor to a sun gear of. a second planetary gear train; a plurality of planet gears meshed with said second sun gear; a plurality of spider shafts carrying said second planet gears, said spider shafts mounted on said spider of said first named planetary gear train; a ring gear meshing with said second named planetary. gears; a one-way brake carried by said second named ring gear assembly arranged for transmitting torque from said ring gear to said fixed supporting housing only in it ranged for manually locking said spider to'said fixed supporting housing; a brake arranged for locking said first named ring gear to said fixed housing; and a control lever and cooperating to speed the engine 5 tral operation.

housing for reverse operation, couple said spider shaft with said driven shaft and lock said first named ring gear to said iixed housing for low operation, and release said driven shaft for neu- DAVID BIERMANN. 

